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211.
Paola Peluso Victor Mamane Emmanuel Aubert Sergio Cossu 《Journal of separation science》2013,36(18):2993-3003
The HPLC enantioseparation of nine atropisomeric 3,3′,5,5′‐tetrasubstituted‐4,4′‐bipyridines was performed in normal and polar organic (PO) phase modes using two immobilized polysaccharide‐based chiral columns, namely, Chiralpak IA and Chiralpak IC. The separation of all racemic analytes, the effect of the chiral selector, and mobile phase (MP) composition on enantioseparation and the enantiomer elution order (EEO) were studied. The beneficial effect of nonstandard solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), and methyl t‐butyl ether on enantioseparation was investigated. All selected 4,4′‐bipyridines were successfully enantioseparated on Chiralpak IA under normal or PO MPs with separation factors from 1.14 to 1.70 and resolutions from 1.3 to 6.5. Two bipyridines were enantioseparated at the multimilligram level on Chiralpak IA. Differently, Chiralpak IC was less versatile toward the considered class of compounds and only five bipyridines out of nine could be efficiently separated. In particular, on these columns, the ternary mixture n‐heptane/THF/DCM (90:5:5) as MP had a positive effect on enantioseparation. An interesting phenomenon of reversal of the EEO depending on the composition of the MP for the 3,3′‐dibromo‐5,5′‐bis‐(E)‐phenylethenyl‐4,4′‐bipyridine along with an exceptional enantioseparation for the 3,3′‐dibromo‐5,5′‐bis‐ferrocenylethynyl‐4,4′‐bipyridine (α = 8.33, Rs = 30.6) were observed on Chiralpak IC. 相似文献
212.
Mohamed Abboud Victor Mamane Emmanuel Aubert 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(1):56-60
The crystal packing of the title compound, C24H18Br2N2S2, is rationalized using the PIXEL method, which allows a separation of the intermolecular interaction energy into Coulombic, polarization, dispersion and repulsion contributions. Infinite (01) molecular planes are formed through π–π stacking and other minor interactions, including a Br...S contact, with the σ hole of the Br atom pointing towards the S‐atom lone pair. The title compound has crystallographically imposed twofold symmetry, with the twofold axis at the mid‐point of the central C—C bond. 相似文献
213.
214.
Carlos Victor Montefusco-Pereira Maria José de Carvalho Ana Paula de Araújo Boleti Lorisa Simas Teixeira Humberto Reis Matos Emerson Silva Lima 《Applied biochemistry and biotechnology》2013,170(6):1367-1378
Diabetes mellitus is a metabolic disease characterized by abnormally high plasma glucose levels, leading to major complications, such as insulin resistance, obesity, hyperlipidemia, and hypertension, also with alterations in the immune and neuronal systems. Brazilian plants have been studied as important sources for new molecules with medicinal properties. The genus Passiflora known as “Maracujá” has been used as a traditional folk medicine for a long time, so an investigation was performed regarding an endemic kind of passion fruit (Passiflora nitida Kunth) from Amazonas, Brazil. Here, we aimed to determine its potential biological activity against metabolic syndrome, oxidative stress, pain, and inflammation. The hydroethanol leaf extract revealed an in vitro α-glucosidase inhibitory activity of 50 % inhibitory concentration (IC50)?=?6.78?±?0.31 μg/mL and an α-amylase inhibition of IC50?=?93.36?±?4.37. In vivo, experiments of different saccharide tolerance resulted in significant glycemia control and, with alloxan-diabetic mice, resulted in a decrease of total cholesterol, a hypoglycemic effect, and an antioxidant activity by thiobarbituric acid-reactive substances measurement. Also, it decreased the carrageenan-induced edema volume and the rate of writhing as a nociceptive response. These results indicate positive effects of P. nitida extract and its potential to inhibit metabolic syndrome. 相似文献
215.
Victor Starov 《Colloid and polymer science》2013,291(2):261-270
A theory of contact angle hysteresis on smooth, homogeneous solid substrates is developed in terms of shape of disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θ r?<?θ?<?θ a, which are different from the unique equilibrium contact angle θ?≠?θ e, correspond to the state of slow “microscopic” advancing or receding motion of the liquid if θ e ?<?θ?<?θ a or θ r?<?θ?<?θ e, respectively. This “microscopic” motion almost abruptly becomes fast “macroscopic” advancing or receding motion after the contact angle reaches the critical values θ?=?θ a or θ r?=?θ, correspondingly. The values of the static receding, θ r, and static advancing, θ a, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining pressure isotherm. It is shown that an advancing contact angle of a droplet on a solid substrate depends on the drop volume and is not a unique characteristic of the liquid–solid system. The suggested mechanism of contact angle hysteresis has direct experimental confirmation. 相似文献
216.
Prof. Evgeny A. Kataev Dr. Grigory V. Kolesnikov Rene Arnold Herman V. Lavrov Prof. Victor N. Khrustalev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3710-3714
Inorganic anions were used as templates in the reaction between a diamine and an activated diacid to form macrocyclic amides. The reaction conditions were found to perform the macrocyclization sufficiently slow to observe a template effect. A number of analytical methods were used to clarify the reaction mechanisms and to show that the structure of the intermediate plays a decisive role in determining the product distribution. For the macrocyclization under kinetic control, it was shown that the amount of a template, the conformational rigidity of building blocks, and the anion affinities of reaction components and intermediates are important parameters that one should take into consideration to achieve high yields. 相似文献
217.
Nataliya A. Samoylova Nikita M. Belov Victor A. Brotsman Dr. Ilya N. Ioffe Dr. Natalia S. Lukonina Dr. Vitaliy Yu. Markov Dr. Adrian Ruff Alexey V. Rybalchenko Paul Schuler Olesya O. Semivrazhskaya Prof. Dr. Bernd Speiser Prof. Dr. Sergey I. Troyanov Prof. Dr. Tatiana V. Magdesieva Dr. Alexey A. Goryunkov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(52):17969-17979
Novel difluoromethylenated [70]fullerene derivatives, C70(CF2)n (n=1–3), were obtained by the reaction of C70 with sodium difluorochloroacetate. Two major products, isomeric C70(CF2) mono‐adducts with [6,6]‐open and [6,6]‐closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X‐ray analysis and high‐level spectroscopic techniques. The [6,6]‐open isomer of C70(CF2) constitutes the first homofullerene example of a non‐hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C70(CF2) isomers showed that it is substantially higher for the [6,6]‐open isomer (the 70‐electron π‐conjugated system is retained) than the [6,6]‐closed form, the latter being similar to the electron affinity of pristine C70. In situ ESR spectroelectrochemical investigation of the C70(CF2) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter‐conversion between the [6,6]‐closed and [6,6]‐open forms of a cage‐modified fullerene driven by an electrochemical one‐electron transfer. Thus, [6,6]‐closed C70(CF2) constitutes an interesting example of a redox‐switchable fullerene derivative. 相似文献
218.
219.
Phu T. Van Victor Bass Dan Shiwarski Frederick Lanni Jonathan Minden 《Electrophoresis》2014,35(18):2642-2655
A current challenge for proteomics is detecting proteins over the large concentration ranges found in complex biological samples such as whole‐cell extracts. Currently, no unbiased, whole‐proteome analysis scheme is capable of detecting the full range of cellular proteins. This is due in part to the limited dynamic range of the detectors used to sense proteins or peptides. We present a new technology, structured illumination (SI) gel imager, which detects fluorescently labeled proteins in electrophoretic gels over a 1 000 000‐fold concentration range. SI uses computer‐generated masks to attenuate the illumination of highly abundant proteins, allowing for long exposures of low‐abundance proteins, thus avoiding detector saturation. A series of progressively masked gel images are assembled into a single, very high dynamic range image. We demonstrate that the SI imager can detect proteins over a concentration range of approximately 1 000 000‐fold, making it a useful tool for comprehensive, unbiased proteome‐wide surveys. 相似文献
220.
Stanislav N. Naryzhny Andrey V. Lisitsa Victor G. Zgoda Elena A. Ponomarenko Alexander I. Archakov 《Electrophoresis》2014,35(6):895-900
Insufficient sensitivity of methods for detection of proteins at a single molecule level does not yet allow obtaining the whole image of human proteome. But to go further, we need at least to know the proteome size, or how many different protein species compose this proteome. This is the task that could be at least partially realized by the method described in this article. The approach used in our study is based on detection of protein spots in 2DE after staining by protein dyes with various sensitivities. As the different protein spots contain different protein species, counting the spots opens a way for estimation of number of protein species. The function representing the dependence of the number of protein spots on sensitivity or LOD of protein dyes was generated. And extrapolation of this function curve to theoretical point of the maximum sensitivity (detection of a single smallest polypeptide) allowed to counting the number of different molecules (polypeptide species) at the concentration level of a single polypeptide per proteome. Using this approach, it was estimated that the minimal numbers of protein species for model objects, Escherichia coli and Pirococcus furiosus, are 6200 and 3400, respectively. We expect a single human cell (HepG2) to contain minimum 70 000 protein species. 相似文献